Moo.com created this interactive game a few years ago that lets you make your own funky Christmas music.  You can now add your own voice or that of someone you know, making things even more fun!

Just click on pictures that represent different instruments and every time you click the picture, you add or take away an instrument.  It's really fun to play around with.

There are 20 instruments to choose from and hundreds of different musical configurations.  It's addicting!